1. Field of the Invention
The present invention relates to a maximum a posteriori (MAP) decoding apparatus and method for efficiently selecting a surviving path.
2. Description of the Related Art
In long distance communication, a maximum likelihood (ML) transceiving device is used as an optimal method for detecting a received signal.
When an ML receiving device allocates a plurality of of bits per symbol in consideration of a length of transmission sequence and high efficiency transmission, it is almost impractical to implement such an ML receiving device since hardware complexity and a calculation amount are increased non-linearly.
A maximum a posteriori (MAP) decoding apparatus calculates all metrics of paths connected to individual state nodes per trellis section. Since the calculation is performed in both directions, that is, forward and backward, complexity may be further increased.
To reduce the complexity in the MAP decoding apparatus, a Log MAP method and a Max-Log MAP decoding method have been introduced. The Max-Log MAP decoding apparatus calculates all metrics of paths connected to individual state nodes per trellis section and then reflects a path having a maximum value to a next trellis section.
Although the complexity is relatively reduced in the Max-Log decoding apparatus, since calculation of the all metrics of the paths connected to the state nodes per trellis section is still performed, the complexity matter still remains unsatisfactory.